Modern day vehicles include a variety of electronic components that increase driver safety and convenience. Rain sensors for automatically activating windshield wipers are one such component. Many rain sensors are optical devices that utilize internal reflection of light from a windshield. Raindrops on a windshield change the amount of reflected light and such information is used for automatically controlling the windshield wipers.
One drawback associated with current rain sensors is that they require prisms and collimating lenses to guide light at an appropriate angle to realize the total internal reflection conditions required for such devices to operate as designed. Lenses, prisms and optical coupling elements require additional space and increase the number of components and expense of such devices.
Another drawback associated with known rain sensing devices is that they are typically not capable of detecting a continuous water film or a coating on a windshield. The way in which the internal reflection arrangements of known sensors operate typically depends upon individual raindrops contacting the windshield and a broader coating of water may not be detectable.
It would be useful to provide a rain sensor for use in connection with a vehicle windshield wiper system that is lower cost, requires less space and provides more robust rain sensing.